CCR5 as a treatment target in pulmonary arterial hypertension

Inhibition of DYRK1A attenuates vascular remodeling in pulmonary arterial hypertension via suppressing STAT3/Pim-1/NFAT pathway

Pulmonary arterial hypertension (PAH) is characterized by progressive vascular remodeling caused by the excessive proliferation and survival of pulmonary artery smooth muscle cells (PASMCs). Dual-specificity tyrosine regulated kinase 1A (DYRK1A) is a pleiotropic kinase involved in the regulation of multiple biological functions, including cell proliferation and survival. However, the role and underlying mechanisms of DYRK1A in PAH pathogenesis remain unclear. We found that DYRK1A was upregulated in PASMCs in response to hypoxia, both in vivo and in vitro. Inhibition of DYRK1A by harmine significantly attenuated hypoxia-induced pulmonary hypertension and pulmonary artery remodeling. Mechanistically, we found that DYRK1A promoted pulmonary arterial remodeling by enhancing the proliferation and survival of PASMCs through activating the STAT3/Pim-1/NFAT pathway, because STAT3 gain-of-function via adeno-associated virus serotype 2 (AAV2) carrying the constitutively active form of STAT3 (STAT3C) nearly abolished the protective effect of harmine on PAH. Collectively, our results reveal a significant role for DYRK1A in pulmonary arterial remodeling and suggest it as a drug target with translational potential for the treatment of PAH.

Extrapulmonary manifestations of pulmonary arterial hypertension

INTRODUCTION

Extrapulmonary manifestations of pulmonary arterial hypertension (PAH) may play a critical pathobiological role and a deeper understanding will advance insight into mechanisms and novel therapeutic targets. This manuscript reviews our understanding of extrapulmonary manifestations of PAH.

AREAS COVERED

A group of experts was assembled and a complimentary PubMed search performed (October 2023 - March 2024). Inflammation is observed throughout the central nervous system and attempts at manipulation are an encouraging step toward novel therapeutics. Retinal vascular imaging holds promise as a noninvasive method of detecting early disease and monitoring treatment responses. PAH patients have gut flora alterations and dysbiosis likely plays a role in systemic inflammation. Despite inconsistent observations, the roles of obesity, insulin resistance and dysregulated metabolism may be illuminated by deep phenotyping of body composition. Skeletal muscle dysfunction is perpetuated by metabolic dysfunction, inflammation, and hypoperfusion, but exercise training shows benefit. Renal, hepatic, and bone marrow abnormalities are observed in PAH and may represent both end-organ damage and disease modifiers.

EXPERT OPINION

Insights into systemic manifestations of PAH will illuminate disease mechanisms and novel therapeutic targets. Additional study is needed to understand whether extrapulmonary manifestations are a cause or effect of PAH and how manipulation may affect outcomes.

Neutrophil extracellular traps promote proliferation of pulmonary smooth muscle cells mediated by CCDC25 in pulmonary arterial hypertension

BACKGROUND

Previous studies have indicated that neutrophil extracellular traps (NETs) play a pivotal role in pathogenesis of pulmonary arterial hypertension (PAH). However, the specific mechanism underlying the impact of NETs on pulmonary artery smooth muscle cells (PASMCs) has not been determined. The objective of this study was to elucidate underlying mechanisms through which NETs contribute to progression of PAH.

METHODS

Bioinformatics analysis was employed in this study to screen for potential molecules and mechanisms associated with occurrence and development of PAH. These findings were subsequently validated in human samples, coiled-coil domain containing 25 (CCDC25) knockdown PASMCs, as well as monocrotaline-induced PAH rat model.

RESULTS

NETs promoted proliferation of PASMCs, thereby facilitating pathogenesis of PAH. This phenomenon was mediated by the activation of transmembrane receptor CCDC25 on PASMCs, which subsequently activated ILK/β-parvin/RAC1 pathway. Consequently, cytoskeletal remodeling and phenotypic transformation occur in PASMCs. Furthermore, the level of NETs could serve as an indicator of PAH severity and as potential therapeutic target for alleviating PAH.

CONCLUSION

This study elucidated the involvement of NETs in pathogenesis of PAH through their influence on the function of PASMCs, thereby highlighting their potential as promising targets for the evaluation and treatment of PAH.

Pulmonary arterial hypertension nanotherapeutics: New pharmacological targets and drug delivery strategies

Pulmonary arterial hypertension (PAH) is a rare, serious, and incurable disease characterized by high lung pressure. PAH-approved drugs based on conventional pathways are still not exhibiting favorable therapeutic outcomes. Drawbacks like short half-lives, toxicity, and teratogenicity hamper effectiveness, clinical conventionality, and long-term safety. Hence, approaches like repurposing drugs targeting various and new pharmacological cascades and/or loaded in non-toxic/efficient nanocarrier systems are being investigated lately. This review summarizes the status of conventional, repurposed, either in vitro, in vivo, and/or in clinical trials of PAH treatment. In-depth description, discussion, and classification of the new pharmacological targets and nanomedicine strategies with a description of all the nanocarriers that showed promising efficiency in delivering drugs are discussed. Ultimately, an illustration of the different nucleic acids tailored and nanoencapsulated within different types of nanocarriers to restore the pathways affected by this disease is presented.

Cysteine-cysteine Chemokine Receptor Type 5 Plays a Critical Role in Exercise Performance by Regulating Mitochondrial Content in Skeletal Muscle

Cysteine-cysteine chemokine receptor type 5 (CCR5) is thought to play an important role in the trafficking of lymphoid cells but has recently also been associated with AMPK signaling pathways that are implicated in energy metabolism in skeletal muscle. We hypothesized that genetic deletions of CCR5 would alter mitochondria content and exercise performance in mice. CCR5-/- and wild-type mice with the same genetic background were subjected to endurance exercise and grip strength tests. The soleus muscle was stained with immunofluorescence for myosin heavy chain 7 (MYH7) and succinate dehydrogenase (SDH) analysis as well as the expression of genes associated with muscle atrophy and mitochondrial oxidative phosphorylation were measured using qPCR. Although there were no differences in the weight of the soleus muscle between the CCR5-/- group and the wild-type mice, the CCR5-/- mice showed the following muscular dysfunctions: (i) decreased MYH7 percentage and cross-section area, (ii) higher myostatin and atrogin-1 mRNA levels, (iii) dropped expression of mitochondrial DNA-encoded electron respiratory chain genes (cytochrome B, cytochrome c oxidase subunit III, and ATP synthase subunit 6) as well as mitochondrial generation genes (PPARγ and PGC-1α), and (iv) lower SDH activity and exercise performance when compared with wild-type mice. In addition, genes associated with mitochondrial biogenesis (PGC-1α, PPARγ, and MFN2) and mitochondrial complex (ND4 and Cytb) were upregulated when the skeletal muscle cell line C2C12 was exposed to cysteine-cysteine chemokine ligand 4 (a ligand of CCR5) in vitro. These findings suggested that attenuation of endurance exercise performance is related to the loss of mitochondrial content and lower SDH activity of soleus muscle in CCR5 knockout mice. The present study provides evidence indicating that the chemokine receptor CCR5 might modulate the skeletal muscle metabolic energy system during exercise.

CC chemokines Modulate Immune responses in Pulmonary Hypertension

BACKGROUND

Pulmonary hypertension (PH) represents a progressive condition characterized by the remodeling of pulmonary arteries, ultimately culminating in right heart failure and increased mortality rates. Substantial evidence has elucidated the pivotal role of perivascular inflammatory factors and immune dysregulation in the pathogenesis of PH. Chemokines, a class of small secreted proteins, exert precise control over immune cell recruitment and functionality, particularly with respect to their migration to sites of inflammation. Consequently, chemokines emerge as critical drivers facilitating immune cell infiltration into the pulmonary tissue during inflammatory responses. This review comprehensively examines the significant contributions of CC chemokines in the maintenance of immune cell homeostasis and their pivotal role in regulating inflammatory responses. The central focus of this discussion is directed towards elucidating the precise immunoregulatory actions of CC chemokines concerning various immune cell types, including neutrophils, monocytes, macrophages, lymphocytes, dendritic cells, mast cells, eosinophils, and basophils, particularly in the context of pH processes. Furthermore, this paper delves into an exploration of the underlying pathogenic mechanisms that underpin the development of PH. Specifically, it investigates processes such as cellular pyroptosis, examines the intricate crosstalk between bone morphogenetic protein receptor type 2 (BMPR2) mutations and the immune response, and sheds light on key signaling pathways involved in the inflammatory response. These aspects are deemed critical in enhancing our understanding of the complex pathophysiology of PH. Moreover, this review provides a comprehensive synthesis of findings from experimental investigations targeting immune cells and CC chemokines.

AIM OF REVIEW

In summary, the inquiry into the inflammatory responses mediated by CC chemokines and their corresponding receptors, and their potential in modulating immune reactions, holds promise as a prospective avenue for addressing PH. The potential inhibition of CC chemokines and their receptors stands as a viable strategy to attenuate the inflammatory cascade and ameliorate the pathological manifestations of PH. Nonetheless, it is essential to acknowledge the current state of clinical trials and the ensuing progress, which regrettably appears to be less than encouraging. Substantial hurdles exist in the successful translation of research findings into clinical applications. The intention is that such emphasis could potentially foster the advancement of potent therapeutic agents presently in the process of clinical evaluation. This, in turn, may further bolster the potential for effective management of PH.

Inflammation and immunity in the pathogenesis of hypoxic pulmonary hypertension

Hypoxic pulmonary hypertension (HPH) is a complicated vascular disorder characterized by diverse mechanisms that lead to elevated blood pressure in pulmonary circulation. Recent evidence indicates that HPH is not simply a pathological syndrome but is instead a complex lesion of cellular metabolism, inflammation, and proliferation driven by the reprogramming of gene expression patterns. One of the key mechanisms underlying HPH is hypoxia, which drives immune/inflammation to mediate complex vascular homeostasis that collaboratively controls vascular remodeling in the lungs. This is caused by the prolonged infiltration of immune cells and an increase in several pro-inflammatory factors, which ultimately leads to immune dysregulation. Hypoxia has been associated with metabolic reprogramming, immunological dysregulation, and adverse pulmonary vascular remodeling in preclinical studies. Many animal models have been developed to mimic HPH; however, many of them do not accurately represent the human disease state and may not be suitable for testing new therapeutic strategies. The scientific understanding of HPH is rapidly evolving, and recent efforts have focused on understanding the complex interplay among hypoxia, inflammation, and cellular metabolism in the development of this disease. Through continued research and the development of more sophisticated animal models, it is hoped that we will be able to gain a deeper understanding of the underlying mechanisms of HPH and implement more effective therapies for this debilitating disease.

gp120 Envelope Glycoproteins of HIV-1 Group M Subtype A and Subtype B Differentially Affect Gene Expression in Human Vascular Endothelial Cells

Cardiovascular complications are seen among human immunodeficiency virus (HIV)-positive individuals, who now survive longer due to successful antiretroviral therapies. Pulmonary arterial hypertension (PAH) is a fatal disease characterized by increased blood pressure in the lung circulation. The prevalence of PAH in the HIV-positive population is dramatically higher than that in the general population. While HIV-1 Group M Subtype B is the most prevalent subtype in western countries, the majority of HIV-1 infections in eastern Africa and former Soviet Union countries are caused by Subtype A. Research on vascular complications in the HIV-positive population in the context of subtype differences, however, has not been rigorous. Much of the research on HIV has focused on Subtype B, and information on the mechanisms of Subtype A is nonexistent. The lack of such knowledge results in health disparities in the development of therapeutic strategies to prevent/treat HIV complications. The present study examined the effects of HIV-1 gp120 of Subtypes A and B on human pulmonary artery endothelial cells by performing protein arrays. We found that the gene expression changes caused by gp120s of Subtypes A and B are different. Subtype A is a more potent downregulator of perostasin, matrix metalloproteinase-2, and ErbB than Subtype B, while Subtype B is more effective in downregulating monocyte chemotactic protein-2 (MCP-2), MCP-3, and thymus- and activation-regulated chemokine proteins. This is the first report of gp120 proteins affecting host cells in an HIV subtype-specific manner, opening up the possibility that complications occur differently in HIV patients throughout the world.

gp120 envelope glycoproteins of HIV-1 Group M Subtype A and Subtype B differentially affect gene expression in human vascular endothelial cells

Cardiovascular complications are seen among human immunodeficiency virus (HIV)-positive individuals who can now survive longer due to successful antiretroviral therapies. Among them, pulmonary arterial hypertension (PAH) is a fatal disease characterized by increased blood pressure in the lung circulation due to vasoconstriction and vascular wall remodeling, resulting in the overworking of the heart. The prevalence of PAH in the HIVpositive population is dramatically higher than that in the general population. While HIV-1 Group M Subtype B is the most prevalent subtype in western countries, the majority of HIV-1 infections in eastern Africa and former Soviet Union countries are caused by Subtype A. Research on the mechanism of vascular complications in the HIV-positive population, especially in the context of subtype differences, however, has not been rigorous. Much of the research on HIV has focused on Subtype B and information on the molecular mechanisms of Subtype A is non-existent. The lack of such knowledge results in health disparities in the development of therapeutic strategies to prevent/treat HIV complications. The present study examined the effects of HIV-1 viral fusion protein gp120 of Subtypes A and B on cultured human pulmonary artery endothelial cells by performing protein arrays. We found that the gene expression changes caused by the gp120s of Subtypes A and B are different. Specifically, Subtype A is a more potent downregulator of perostasin, matrix metalloproteinase-2 (MMP-2), and ErbB/Her3 than Subtype B, while Subtype B is more effective in downregulating monocyte chemotactic protein-2 (MCP-2/CCL8), MCP-3 (CCL7), and thymus- and activation-regulated chemokine (TARC/CCL17) proteins. This is the first report of gp120 proteins affecting host cells in an HIV subtype-specific manner, opening up the possibility that vascular complications may occur differently in HIV patients throughout the world.

Pathophysiology and new advances in pulmonary hypertension

Pulmonary hypertension is a progressive and often fatal cardiopulmonary condition characterised by increased pulmonary arterial pressure, structural changes in the pulmonary circulation, and the formation of vaso-occlusive lesions. These changes lead to increased right ventricular afterload, which often progresses to maladaptive right ventricular remodelling and eventually death. Pulmonary arterial hypertension represents one of the most severe and best studied types of pulmonary hypertension and is consistently targeted by drug treatments. The underlying molecular pathogenesis of pulmonary hypertension is a complex and multifactorial process, but can be characterised by several hallmarks: inflammation, impaired angiogenesis, metabolic alterations, genetic or epigenetic abnormalities, influence of sex and sex hormones, and abnormalities in the right ventricle. Current treatments for pulmonary arterial hypertension and some other types of pulmonary hypertension target pathways involved in the control of pulmonary vascular tone and proliferation; however, these treatments have limited efficacy on patient outcomes. This review describes key features of pulmonary hypertension, discusses current and emerging therapeutic interventions, and points to future directions for research and patient care. Because most progress in the specialty has been made in pulmonary arterial hypertension, this review focuses on this type of pulmonary hypertension. The review highlights key pathophysiological concepts and emerging therapeutic directions, targeting inflammation, cellular metabolism, genetics and epigenetics, sex hormone signalling, bone morphogenetic protein signalling, and inhibition of tyrosine kinase receptors.

Role of macrophages in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a severe cardiopulmonary vascular disease characterized by progressive pulmonary artery pressure elevation, increased pulmonary vascular resistance and ultimately right heart failure. Studies have demonstrated the involvement of multiple immune cells in the development of PAH in patients with PAH and in experimental PAH. Among them, macrophages, as the predominant inflammatory cells infiltrating around PAH lesions, play a crucial role in exacerbating pulmonary vascular remodeling in PAH. Macrophages are generally polarized into (classic) M1 and (alternative) M2 phenotypes, they accelerate the process of PAH by secreting various chemokines and growth factors (CX3CR1, PDGF). In this review we summarize the mechanisms of immune cell action in PAH, as well as the key factors that regulate the polarization of macrophages in different directions and their functional changes after polarization. We also summarize the effects of different microenvironments on macrophages in PAH. The insight into the interactions between macrophages and other cells, chemokines and growth factors may provide important clues for the development of new, safe and effective immune-targeted therapies for PAH.

Pulmonary hypertension: Linking inflammation and pulmonary arterial stiffening

Pulmonary hypertension (PH) is a progressive disease that arises from multiple etiologies and ultimately leads to right heart failure as the predominant cause of morbidity and mortality. In patients, distinct inflammatory responses are a prominent feature in different types of PH, and various immunomodulatory interventions have been shown to modulate disease development and progression in animal models. Specifically, PH-associated inflammation comprises infiltration of both innate and adaptive immune cells into the vascular wall of the pulmonary vasculature—specifically in pulmonary vascular lesions—as well as increased levels of cytokines and chemokines in circulating blood and in the perivascular tissue of pulmonary arteries (PAs). Previous studies suggest that altered hemodynamic forces cause lung endothelial dysfunction and, in turn, adherence of immune cells and release of inflammatory mediators, while the resulting perivascular inflammation, in turn, promotes vascular remodeling and the progression of PH. As such, a vicious cycle of endothelial activation, inflammation, and vascular remodeling may develop and drive the disease process. PA stiffening constitutes an emerging research area in PH, with relevance in PH diagnostics, prognostics, and as a therapeutic target. With respect to its prognostic value, PA stiffness rivals the well-established measurement of pulmonary vascular resistance as a predictor of disease outcome. Vascular remodeling of the arterial extracellular matrix (ECM) as well as vascular calcification, smooth muscle cell stiffening, vascular wall thickening, and tissue fibrosis contribute to PA stiffening. While associations between inflammation and vascular stiffening are well-established in systemic vascular diseases such as atherosclerosis or the vascular manifestations of systemic sclerosis, a similar connection between inflammatory processes and PA stiffening has so far not been addressed in the context of PH. In this review, we discuss potential links between inflammation and PA stiffening with a specific focus on vascular calcification and ECM remodeling in PH.

Single-Cell RNA-Sequencing Reveals the Active Involvement of Macrophage Polarizations in Pulmonary Hypertension

Background. Sustained hypoxia can trigger a progressive rise in pulmonary artery pressure and cause serious pulmonary diseases. Macrophages play important roles along the progression of pulmonary hypertension. However, the state of macrophage polarization during the early stage of pulmonary hypertension is unclear. Methods. Unlike traditional sequencing method, single-cell sequencing can accurately distinguish among cell types and better understand cell-to-cell relationships. In this study, we investigated the polarization of macrophages in pulmonary hypertension via single-cell RNA-sequencing in a mice hypoxia model, which was then validated in patients with pulmonary hypertension. Results. We identified that the intermittent exposure to hypoxic conditions could lead to the production of more M2-type macrophages than M1-type macrophages in a mouse model. Further validation analysis was performed by analyzing lung tissue of patients with pulmonary hypertension, revealing that the number of disease-associated M2 macrophages was substantially increased. Conclusions. In this study, the active anti-inflammatory response of macrophage involved in pulmonary hypertension has been identified, suggesting that intervention against the polarization of macrophages to the M2 type may be a potential way to reduce chronic pulmonary inflammation, pulmonary vascular remodeling, and artery pressure. Thus, investigation of macrophage polarization associated with hypoxia could help us better understand disease mechanism and craft effective prevention strategies and approaches.

Rationale of using the dual chemokine receptor CCR2/CCR5 inhibitor cenicriviroc for the treatment of COVID-19

Coronavirus Disease 2019 (COVID-19), caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), has created a global pandemic infecting over 230 million people and costing millions of lives. Therapies to attenuate severe disease are desperately needed. Cenicriviroc (CVC), a C-C chemokine receptor type 5 (CCR5) and C-C chemokine receptor type 2 (CCR2) antagonist, an agent previously studied in advanced clinical trials for patients with HIV or nonalcoholic steatohepatitis (NASH), may have the potential to reduce respiratory and cardiovascular organ failures related to COVID-19. Inhibiting the CCR2 and CCR5 pathways could attenuate or prevent inflammation or fibrosis in both early and late stages of the disease and improve outcomes of COVID-19. Clinical trials using CVC either in addition to standard of care (SoC; e.g., dexamethasone) or in combination with other investigational agents in patients with COVID-19 are currently ongoing. These trials intend to leverage the anti-inflammatory actions of CVC for ameliorating the clinical course of COVID-19 and prevent complications. This article reviews the literature surrounding the CCR2 and CCR5 pathways, their proposed role in COVID-19, and the potential role of CVC to improve outcomes.

Olive phenols preserve lamin B1 expression reducing cGAS/STING/NFκB-mediated SASP in ionizing radiation-induced senescence

Senescence occurs upon critical telomere shortening, or following DNA damage, oncogenic activation, hypoxia and oxidative stress, overall referred to stress-induced premature senescence (SIPS). In response to DNA damage, senescent cells release cytoplasmic chromatin fragments (CCFs), and express an altered secretome, the senescence-associated secretory phenotype (SASP), which contributes to generate a pro-inflammatory and pro-tumoral extracellular milieu. Polyphenols have gained significant attention owing to their anti-inflammatory and anti-tumour activities. Here, we studied the effect of oleuropein aglycone (OLE) and hydroxytyrosol (HT) on DNA damage, CCF appearance and SASP in a model of irradiation-induced senescence. Neonatal human dermal fibroblasts (NHDFs) were γ-irradiated and incubated with OLE, 5 µM and HT, 1 µM. Cell growth and senescence-associated (SA)-β-Gal-staining were used as senescence markers. DNA damage was evaluated by Comet assay, lamin B1 expression, release of CCFs, cyclic GMP-AMP Synthase (cGAS) activation. IL-6, IL-8, MCP-1 and RANTES were measured by ELISA assay. Our results showed that OLE and HT exerted a protective effect on 8 Gy irradiation-induced senescence, preserving lamin B1 expression and reducing cGAS/STING/NFκB-mediated SASP. The ability of OLE and HT to mitigate DNA damage, senescence status and the related SASP in normal cells can be exploited to improve the efficacy and safety of cancer radiotherapy.

Angiotensin-converting enzyme 2 alleviates pulmonary artery hypertension through inhibition of focal adhesion kinase expression

Focal adhesion kinase (FAK) is an important therapeutic target in pulmonary artery hypertension (PAH); however, the mechanism of its activation remains unknown. The present study aimed to investigate whether angiotensin-converting enzyme 2 (ACE2) could regulate FAK and alleviate PAH in a rat model of PAH established with a single administration of monocrotaline followed by continuous hypoxia treatment. In the current study, right ventricular pressure, body weight and the right ventricular hypertrophy index were measured, and hematoxylin-eosin staining was performed on lung tissues to determine whether the modeling was successful. Changes in the serum levels of FAK were measured using an ELISA kit to evaluate the association between ACE2 and FAK. The mRNA expression levels of ACE2, FAK, caspase-3 and survivin were determined using reverse transcription-quantitative PCR (RT-qPCR). The protein expression levels of ACE2, phosphorylated FAK/FAK, cleaved caspase-3/pro-caspase-3 and survivin were determined via western blotting. Immunohistochemistry was applied to detect the expression of FAK around the pulmonary arterioles. Apoptosis of smooth muscle cells around pulmonary arterioles was observed by TUNEL staining. After treatment with the ACE2 activator DIZE or inhibitor DX-600, the results demonstrated that ACE2 reduced PAH-induced changes in arteriole morphology compared with the control. It also inhibited FAK expression in serum. WB and RT-qPCR results suggested that ACE2 inhibited the expression of FAK and pathway-related proteins, and promoted caspase-3 expression. Additionally, ACE2 reduced FAK expression around the pulmonary arterioles and promoted smooth muscle cell apoptosis. The results indicated that ACE2 activation inhibited FAK expression, leading to alleviation of the symptoms of PAH.

P2X7-deficiency improves plasticity and cognitive abilities in a mouse model of Tauopathy

Alzheimer's disease is the most common form of dementia characterized by intracellular aggregates of hyperphosphorylated Tau protein and extracellular accumulation of amyloid β (Aβ) peptides. We previously demonstrated that the purinergic receptor P2X7 (P2X7) plays a major role in Aβ-mediated neurodegeneration but the relationship between P2X7 and Tau remained overlooked. Such a link was supported by cortical upregulation of P2X7 in patients with various type of frontotemporal lobar degeneration, including mutation in the Tau-coding gene, MAPT, as well as in the brain of a Tauopathy mouse model (THY-Tau22). Subsequent phenotype analysis of P2X7-deficient Tau mice revealed the instrumental impact of this purinergic receptor. Indeed, while P2X7-deficiency had a moderate effect on Tau pathology itself, we observed a significant reduction of microglia activation and of Tau-related inflammatory mediators, particularly CCL4. Importantly, P2X7 deletion ultimately rescued synaptic plasticity and memory impairments of Tau mice. Altogether, the present data support a contributory role of P2X7 dysregulation on processes governing Tau-induced brain anomalies. Due to the convergent role of P2X7 blockade in both Aβ and Tau background, P2X7 inhibitors might prove to be ideal candidate drugs to curb the devastating cognitive decline in Alzheimer's disease and Tauopathies.

Screening of Hub Genes Associated with Pulmonary Arterial Hypertension by Integrated Bioinformatic Analysis

Background

Pulmonary arterial hypertension (PAH) is a disease or pathophysiological syndrome which has a low survival rate with abnormally elevated pulmonary artery pressure caused by known or unknown reasons. In addition, the pathogenesis of PAH is not fully understood. Therefore, it has become an urgent matter to search for clinical molecular markers of PAH, study the pathogenesis of PAH, and contribute to the development of new science-based PAH diagnosis and targeted treatment methods.

Methods

In this study, the Gene Expression Omnibus (GEO) database was used to downloaded a microarray dataset about PAH, and the differentially expressed genes (DEGs) between PAH and normal control were screened out. Moreover, we performed the functional enrichment analyses and protein-protein interaction (PPI) network analyses of the DEGs. In addition, the prediction of miRNA and transcriptional factor (TF) of hub genes and construction miRNA-TF-hub gene network were performed. Besides, the ROC curve was used to evaluate the diagnostic value of hub genes. Finally, the potential drug targets for the 5 identified hub genes were screened out.

Results

69 DEGs were identified between PAH samples and normal samples. GO and KEGG pathway analyses revealed that these DEGs were mostly enriched in the inflammatory response and cytokine-cytokine receptor interaction, respectively. The miRNA-hub genes network was conducted subsequently with 131 miRNAs, 7 TFs, and 5 hub genes (CCL5, CXCL12, VCAM1, CXCR1, and SPP1) which screened out via constructing the PPI network. 17 drugs interacted with 5 hub genes were identified.

Conclusions

Through bioinformatic analysis of microarray data sets, 5 hub genes (CCL5, CXCL12, VCAM1, CXCR1, and SPP1) were identified from DEGs between control samples and PAH samples. Studies showed that the five hub genes might play an important role in the development of PAH. These 5 hub genes might be potential biomarkers for diagnosis or targets for the treatment of PAH. In addition, our work also indicated that paying more attention on studies based on these 5 hub genes might help to understand the molecular mechanism of the development of PAH.

Viral Infection and Cardiovascular Disease: Implications for the Molecular Basis of COVID-19 Pathogenesis

The current pandemic of coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). While this respiratory virus only causes mild symptoms in younger healthy individuals, elderly people and those with cardiovascular diseases such as systemic hypertension are susceptible to developing severe conditions that can be fatal. SARS-CoV-2 infection is also associated with an increased incidence of cardiovascular diseases such as myocardial injury, acute coronary syndrome, and thromboembolism. Understanding the mechanisms of the effects of this virus on the cardiovascular system should thus help develop therapeutic strategies to reduce the mortality and morbidity associated with SARS-CoV-2 infection. Since this virus causes severe and fatal conditions in older individuals with cardiovascular comorbidities, effective therapies targeting specific populations will likely contribute to ending this pandemic. In this review article, the effects of various viruses—including other coronaviruses, influenza, dengue, and human immunodeficiency virus—on the cardiovascular system are described to help provide molecular mechanisms of pathologies associated with SARS-CoV-2 infection and COVID-19. The goal is to provide mechanistic information from the biology of other viral infections in relation to cardiovascular pathologies for the purpose of developing improved vaccines and therapeutic agents effective in preventing and/or treating the acute and long-term consequences of SARS-CoV-2 and COVID-19.

Mechanisms of Pulmonary Hypertension in Acute Respiratory Distress Syndrome (ARDS)

Background: Acute respiratory distress syndrome (ARDS) is a severe and often fatal disease. The causes that lead to ARDS are multiple and include inhalation of salt water, smoke particles, or as a result of damage caused by respiratory viruses. ARDS can also arise due to systemic complications such as blood transfusions, sepsis, or pancreatitis. Unfortunately, despite a high mortality rate of 40%, there are limited treatment options available for ARDS outside of last resort options such as mechanical ventilation and extracorporeal support strategies. Aim of review: A complication of ARDS is the development of pulmonary hypertension (PH); however, the mechanisms that lead to PH in ARDS are not fully understood. In this review, we summarize the known mechanisms that promote PH in ARDS. Key scientific concepts of review: (1) Provide an overview of acute respiratory distress syndrome; (2) delineate the mechanisms that contribute to the development of PH in ARDS; (3) address the implications of PH in the setting of coronavirus disease 2019 (COVID-19).

Cytokines, Chemokines, and Inflammation in Pulmonary Arterial Hypertension

According to the World Symposium Pulmonary Hypertension (WSPH) classification, pulmonary hypertension (PH) is classified into five categories based on etiology. Among them, Group 1 pulmonary arterial hypertension (PAH) disorders are rare but progressive and often, fatal despite multiple approved treatments. Elevated pulmonary arterial pressure in patients with WSPH Group 1 PAH is mainly caused by increased pulmonary vascular resistance (PVR), due primarily to sustained pulmonary vasoconstriction and excessive obliterative pulmonary vascular remodeling. Growing evidence indicates that inflammation plays a critical role in the development of pulmonary vascular remodeling associated with PAH. While the role of auto-immunity is unclear, infiltration of inflammatory cells in and around vascular lesions, including T- and B-cells, dendritic cells, macrophages, and mast cells have been observed in PAH patients. Serum and plasma levels of chemokines, cytokines, and autoantibodies are also increased in PAH patients; some of these circulating molecules are correlated with disease severity and survival. Preclinical experiments have reported a key role of the inflammation in PAH pathophysiology in vivo. Importantly, anti-inflammatory and immunosuppressive agents have further exhibited therapeutic effects. The present chapter reviews published experimental and clinical evidence highlighting the canonical role of inflammation in the pathogenesis of PAH and as a major target for the development of anti-inflammatory therapies in patients with PAH.

SARS-CoV-2 Spike Protein and Lung Vascular Cells

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is causing the current pandemic of coronavirus disease 2019 (COVID-19), and COVID-19 vaccines focus on its spike protein. However, in addition to facilitating the membrane fusion and viral entry, the SARS-CoV-2 spike protein promotes cell growth signaling in human lung vascular cells, and patients who have died of COVID-19 have thickened pulmonary vascular walls, linking the spike protein to a fatal disease, pulmonary arterial hypertension (PAH). In addition to SARS-CoV spike proteins, gp120, the viral membrane fusion protein of human immunodeficiency virus (HIV), has been reported to promote cell signaling, and long-term surviving HIV-positive patients have a high incidence of developing PAH. This article describes the findings of the SARS-CoV-2 spike protein affecting lung vascular cells and explains how the spike protein possibly increases the incidence of PAH. Since the SARS-CoV-2 spike protein will be administered to millions of people as COVID-19 vaccines, it is critical to understand the biological effects of this protein on human cells to ensure that it does not promote long-term adverse health consequences.

Perivascular Inflammation in Pulmonary Arterial Hypertension

Perivascular inflammation is a prominent pathologic feature in most animal models of pulmonary hypertension (PH) as well as in pulmonary arterial hypertension (PAH) patients. Accumulating evidence suggests a functional role of perivascular inflammation in the initiation and/or progression of PAH and pulmonary vascular remodeling. High levels of cytokines, chemokines, and inflammatory mediators can be detected in PAH patients and correlate with clinical outcome. Similarly, multiple immune cells, including neutrophils, macrophages, dendritic cells, mast cells, T lymphocytes, and B lymphocytes characteristically accumulate around pulmonary vessels in PAH. Concomitantly, vascular and parenchymal cells including endothelial cells, smooth muscle cells, and fibroblasts change their phenotype, resulting in altered sensitivity to inflammatory triggers and their enhanced capacity to stage inflammatory responses themselves, as well as the active secretion of cytokines and chemokines. The growing recognition of the interaction between inflammatory cells, vascular cells, and inflammatory mediators may provide important clues for the development of novel, safe, and effective immunotargeted therapies in PAH.

The role of macrophages in pulmonary hypertension: Pathogenesis and targeting

Pulmonary hypertension (PH) is a pathophysiological disorder that can complicate most cardiovascular and respiratory diseases and may involve multiple clinical conditions, but its pathogenesis is poorly understood. Despite recent developments in the management of PH, there is an urgent need for new ways to effectively treat PH and reduce the risk of further complications. Recent studies have shown that dysregulated immunity underlies the development of PH. Myeloid cells, including monocytes and macrophages, participate in immune homeostasis and the adaptive immune response, but the function and production of these cells in PH is not well understood. A prominent pathological feature of pH is the accumulation of macrophages near the arterioles of the lung, indicating that pulmonary inflammation mediated by lung perivascular macrophages is a key driver of pulmonary remodelling, which leads to increased right ventricular systolic pressure. An improved understanding of the roles macrophages play in immune responses associated with PH may lead to new therapeutic targets. In this review, we highlight the relationship between macrophages and PH, the molecular mechanisms involved, and the recent advances in targeting these processes to treat PH.

Impact of prolonged maraviroc treatment on non-AIDS-related comorbidities in HIV-positive patients: a retrospective cohort study

OBJECTIVES

This retrospective study evaluates the effect of maraviroc, the first CCR5 receptor antagonist, on non-AIDS-related comorbidity incidence and its impact on inflammatory and lipid parameters.

METHODS

Seventy-four HIV patients on maraviroc treatment were compared with 312 patients never exposed to maraviroc (matched for sex, age and CD4 nadir).

RESULTS

At baseline (T0), maraviroc patients presented a longer duration of HIV infection, a higher prevalence of comorbidities and a greater frequency of polypharmacy. Non-AIDS-defining disease incidence was lower in the maraviroc group than in the non-maraviroc group (without achieving statistical significance). Except triglycerides (TGL), which dropped only in the maraviroc group, inflammatory and immunological parameters did not significantly change in either group by the end of the study period (T3). At T3, high-sensitivity C-reactive protein (hsCRP) and high-density lipoprotein were inversely correlated in both groups (Spearman's rho: maraviroc -0.30, P = 0.05; non-maraviroc -0.23, P = 0.0003). Only in the non-maraviroc group was the positive correlation between hsCRP and lipids observed both at T0 (hsCRP/low-density lipoprotein (LDL) +0.17, P = 0.004; hsCRP/total cholesterol +0.20, P = 0.0007; hsCRP/TGL +0.12, P = 0.04) and T3 (hsCRP/LDL +0.26, P < 0.0001; hsCRP/total cholesterol +0.24, P = 0.0001; hsCRP/TGL +0.15, P = 0.02). These correlations were not found in the maraviroc group. A significant positive correlation was found at T0 and at T3 between hsCRP and D-dimer in both groups (maraviroc: T0 +0.46, P = 0.0007; T3 +0.41, P = 0.006; non-maraviroc: T0 +0.17, P = 0.02; T3: +0.17, P = 0.017).

CONCLUSIONS

These data suggest a possible protective role of maraviroc in the incidence of non-AIDS-related comorbidities in a population with longer-lasting infection and allow us to hypothesize its role in the modulation of lipid-dependent inflammation.

HIV X4 Variants Increase Arachidonate 5-Lipoxygenase in the Pulmonary Microenvironment and are associated with Pulmonary Arterial Hypertension

Pulmonary Arterial Hypertension (PAH) is overrepresented in People Living with Human Immunodeficiency Virus (PLWH). HIV protein gp120 plays a key role in the pathogenesis of HIV-PAH. Genetic changes in HIV gp120 determine viral interactions with chemokine receptors; specifically, HIV-X4 viruses interact with CXCR4 while HIV-R5 interact with CCR5 co-receptors. Herein, we leveraged banked samples from patients enrolled in the NIH Lung HIV studies and used bioinformatic analyses to investigate whether signature sequences in HIV-gp120 that predict tropism also predict PAH. Further biological assays were conducted in pulmonary endothelial cells in vitro and in HIV-transgenic rats. We found that significantly more persons living with HIV-PAH harbor HIV-X4 variants. Multiple HIV models showed that recombinant gp120-X4 as well as infectious HIV-X4 remarkably increase arachidonate 5-lipoxygenase (ALOX5) expression. ALOX5 is essential for the production of leukotrienes; we confirmed that leukotriene levels are increased in bronchoalveolar lavage fluid of HIV-infected patients. This is the first report associating HIV-gp120 genotype to a pulmonary disease phenotype, as we uncovered X4 viruses as potential agents in the pathophysiology of HIV-PAH. Altogether, our results allude to the supplementation of antiretroviral therapy with ALOX5 antagonists to rescue patients with HIV-X4 variants from fatal PAH.

A non-selective endothelin receptor antagonist bosentan modulates kinetics of bone marrow-derived cells in ameliorating pulmonary hypertension in mice

The aim of this study was to investigate whether a dual endothelin receptor antagonist bosentan modulates the kinetics of bone marrow-derived stem cells in inhibiting the development of pulmonary hypertension. Bone marrow chimeric mice, transplanted with enhanced green fluorescent protein (eGFP)-positive bone marrow mononuclear cells, were exposed to hypobaric hypoxia or kept in the ambient air, and were daily treated with bosentan sodium salt or saline for 21 days. After the treatment period, right ventricular pressure was measured and pulmonary vascular morphometry was conducted. Incorporation of bone marrow-derived cells was analyzed by immunohistochemistry. Gene expression and protein level in the lung tissue were evaluated by quantitative real-time PCR and western blotting, respectively. The results showed that, in hypoxic mice, right ventricular pressure and the percentage of muscularized vessel were increased and pulmonary vascular density was decreased, each of which was reversed by bosentan. Bone marrow-derived endothelial cells and macrophages in lungs were increased by hypoxia. Bosentan promoted bone marrow-derived endothelial cell incorporation but inhibited macrophage infiltration into lungs. Quantitative real-time PCR analysis revealed that interleukin 6, stromal cell-derived factor-1, and monocyte chemoattractant protein-1 were upregulated by hypoxia, in which interleukin 6 and monocyte chemoattractant protein-1 were downregulated and stromal cell-derived factor-1 was upregulated by bosentan. Protein level of endothelial nitric oxide synthase (eNOS) in the whole lung was significantly upregulated by hypoxia, which was further upregulated by bosentan. Bosentan modulated kinetics of bone marrow-derived ECs and macrophages and related gene expression in lungs in ameliorating pulmonary hypertension in mice. Altered kinetics of bone marrow-derived stem cells may be a novel mechanism of the endothelin receptor blockade in vivo and confer a new understanding of the therapeutic basis for pulmonary hypertension.

Comprehensive identification of signaling pathways for idiopathic pulmonary arterial hypertension

Whole exome sequencing (WES) was used in the research of familial pulmonary arterial hypertension (FPAH). CAV1 and KCNK3 were found as two novel candidate genes of FPAH. However, few pathogenic genes were identified in idiopathic pulmonary arterial hypertension (IPAH). We conducted WES in 20 unrelated IPAH patients who did not carry the known PAH-pathogenic variants among BMPR2, CAV1, KCNK3, SMAD9, ALK1, and ENG. We found a total of 4,950 variants in 3,534 genes, including 4,444 single-nucleotide polymorphisms and 506 insertions/deletions (InDels). Through the comprehensive and multilevel analysis, we disclosed several novel signaling cascades significantly connected to IPAH, including variants related to cadherin signaling pathway, dilated cardiomyopathy, glucose metabolism, immune response, mucin-type O-glycosylation, phospholipase C (PLC)-activating G protein-coupled receptor (GPCR) signaling pathway, vascular contraction and generation, and voltage-dependent Ca²⁺ channels. We also conducted validation studies in five mutant genes related to PLC-activating GPCR signaling pathway potentially involved in intracellular calcium regulation through Sanger sequencing for mutation accuracy, qRT-PCR for mRNA stability, immunofluorescence for subcellular localization, Western blotting for protein level, Fura-2 imaging for intracellular calcium, and proliferation analysis for cell function. The validation experiments showed that those variants in CCR5 and C3AR1 significantly increased the rise of intracellular calcium and the variant in CCR5 profoundly enhanced proliferative capacity of human pulmonary artery smooth muscle cells. Thus, our study suggests that multiple genetically affected signaling pathways take effect together to cause the formation of IPAH and the development of right heart failure and may further provide new therapy targets or putative clues for the present treatments such as limited therapeutic effectiveness of Ca²⁺ channel blockers.

Transcriptional profiling of lung cell populations in idiopathic pulmonary arterial hypertension

Despite recent improvements in management of idiopathic pulmonary arterial hypertension, mortality remains high. Understanding the alterations in the transcriptome–phenotype of the key lung cells involved could provide insight into the drivers of pathogenesis. In this study, we examined differential gene expression of cell types implicated in idiopathic pulmonary arterial hypertension from lung explants of patients with idiopathic pulmonary arterial hypertension compared to control lungs. After tissue digestion, we analyzed all cells from three idiopathic pulmonary arterial hypertension and six control lungs using droplet-based single cell RNA-sequencing. After dimensional reduction by t-stochastic neighbor embedding, we compared the transcriptomes of endothelial cells, pericyte/smooth muscle cells, fibroblasts, and macrophage clusters, examining differential gene expression and pathways implicated by analysis of Gene Ontology Enrichment. We found that endothelial cells and pericyte/smooth muscle cells had the most differentially expressed gene profile compared to other cell types. Top differentially upregulated genes in endothelial cells included novel genes: ROBO4, APCDD1, NDST1, MMRN2, NOTCH4, and DOCK6, as well as previously reported genes: ENG, ORAI2, TFDP1, KDR, AMOTL2, PDGFB, FGFR1, EDN1, and NOTCH1. Several transcription factors were also found to be upregulated in idiopathic pulmonary arterial hypertension endothelial cells including SOX18, STRA13, LYL1, and ELK, which have known roles in regulating endothelial cell phenotype. In particular, SOX18 was implicated through bioinformatics analyses in regulating the idiopathic pulmonary arterial hypertension endothelial cell transcriptome. Furthermore, idiopathic pulmonary arterial hypertension endothelial cells upregulated expression of FAM60A and HDAC7, potentially affecting epigenetic changes in idiopathic pulmonary arterial hypertension endothelial cells. Pericyte/smooth muscle cells expressed genes implicated in regulation of cellular apoptosis and extracellular matrix organization, and several ligands for genes showing increased expression in endothelial cells. In conclusion, our study represents the first detailed look at the transcriptomic landscape across idiopathic pulmonary arterial hypertension lung cells and provides robust insight into alterations that occur in vivo in idiopathic pulmonary arterial hypertension lungs.

The role of chemokines and chemokine receptors in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterized by progressive pulmonary artery remodelling leading to increased right ventricular pressure overload, which results in right heart failure and premature death. Inflammation plays a central role in the development of PAH, and the recruitment and function of immune cells are tightly regulated by chemotactic cytokines called chemokines. A number of studies have shown that the development and progression of PAH are associated with the dysregulated expression of several chemokines and chemokine receptors in the pulmonary vasculature. Moreover, some chemokines are differentially regulated in the pressure-overloaded right ventricle. Recent studies have tested the efficacy of pharmacological agents targeting several chemokines and chemokine receptors for their effects on the development of PAH, suggesting that these receptors could serve as useful therapeutic targets. In this review, we provide recent insights into the role of chemokines and chemokine receptors in PAH and RV remodelling and the opportunities and roadblocks in targeting them. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.1/issuetoc.

CCR5: Established paradigms and new frontiers for a 'celebrity' chemokine receptor

Because of the level of attention it received due to its role as the principal HIV coreceptor, CCR5 has been described as a 'celebrity' chemokine receptor. Here we describe the development of CCR5 inhibitory strategies that have been developed for HIV therapy and which are now additionally being considered for use in HIV prevention and cure. The wealth of CCR5-related tools that have been developed during the intensive investigation of CCR5 as an HIV drug target can now be turned towards the study of CCR5 as a model chemokine receptor. We also summarize what is currently known about the cell biology and pharmacology of CCR5, providing an update on new areas of investigation that have emerged in recent research. Finally, we discuss the potential of CCR5 as a drug target for diseases other than HIV, discussing the evidence linking CCR5 and its natural chemokine ligands with inflammatory diseases, particularly neuroinflammation, and certain cancers. These pathologies may provide new uses for the strategies for CCR5 blockade originally developed to combat HIV/AIDS.

Cytokines trigger disruption of endothelium barrier function and p38 MAP kinase activation in BMPR2-silenced human lung microvascular endothelial cells

The bone morphogenetic protein receptor II (BMPRII) signaling pathway is impaired in pulmonary arterial hypertension and mutations in the BMPR2 gene have been observed in both heritable and idiopathic pulmonary arterial hypertension. However, all BMPR2 mutation carriers do not develop pulmonary arterial hypertension, and inflammation could trigger the development of the disease in BMPR2 mutation carriers. Circulating levels and/or lung tissue expression of cytokines such as tumor necrosis factor-α or interleukin-18 are elevated in patients with pulmonary arterial hypertension and could be involved in the pathogenesis of pulmonary arterial hypertension. We consequently hypothesized that cytokines could trigger endothelial dysfunction in addition to impaired BMPRII signaling. Our aim was to determine whether impairment of BMPRII signaling might affect endothelium barrier function and adhesiveness to monocytes, in response to cytokines. BMPR2 was silenced in human lung microvascular endothelial cells (HLMVECs) using lentiviral vectors encoding microRNA-based hairpins. Effects of tumor necrosis factor-α and interleukin-18 on HLMVEC adhesiveness to the human monocyte cell line THP-1, adhesion molecule expression, endothelial barrier function and activation of P38MAPK were investigated in vitro. Stable BMPR2 silencing in HLMVECs resulted in impaired endothelial barrier function and constitutive activation of P38MAPK. Adhesiveness of BMPR2-silenced HLMVECs to THP-1 cells was enhanced by tumor necrosis factor-α and interleukin-18 through ICAM-1 adhesion molecule. Interestingly, tumor necrosis factor-α induced activation of P38MAPK and disrupted endothelial barrier function in BMPR2-silenced HLMVECs. Altogether, our findings showed that stable BMPR2 silencing resulted in impaired endothelial barrier function and activation of P38MAPK in HLMVECs. In BMPR2-silenced HLMVECs, cytokines enhanced adhesiveness capacities, activation of P38MAPK and impaired endothelial barrier function suggesting that cytokines could trigger the development of pulmonary arterial hypertension in a context of impaired BMPRII signaling pathway.

Dynamic and diverse changes in the functional properties of vascular smooth muscle cells in pulmonary hypertension

Pulmonary hypertension (PH) is the end result of interaction between pulmonary vascular tone and a complex series of cellular and molecular events termed 'vascular remodelling'. The remodelling process, which can involve the entirety of pulmonary arterial vasculature, almost universally involves medial thickening, driven by increased numbers and hypertrophy of its principal cellular constituent, smooth muscle cells (SMCs). It is noted, however that SMCs comprise heterogeneous populations of cells, which can exhibit markedly different proliferative, inflammatory, and extracellular matrix production changes during remodelling. We further consider that these functional changes in SMCs of different phenotype and their role in PH are dynamic and may undergo significant changes over time (which we will refer to as cellular plasticity); no single property can account for the complexity of the contribution of SMC to pulmonary vascular remodelling. Thus, the approaches used to pharmacologically manipulate PH by targeting the SMC phenotype(s) must take into account processes that underlie dominant phenotypes that drive the disease. We present evidence for time- and location-specific changes in SMC proliferation in various animal models of PH; we highlight the transient nature (rather than continuous) of SMC proliferation, emphasizing that the heterogenic SMC populations that reside in different locations along the pulmonary vascular tree exhibit distinct responses to the stresses associated with the development of PH. We also consider that cells that have often been termed 'SMCs' may arise from many origins, including endothelial cells, fibroblasts and resident or circulating progenitors, and thus may contribute via distinct signalling pathways to the remodelling process. Ultimately, PH is characterized by long-lived, apoptosis-resistant SMC. In line with this key pathogenic characteristic, we address the acquisition of a pro-inflammatory phenotype by SMC that is essential to the development of PH. We present evidence that metabolic alterations akin to those observed in cancer cells (cytoplasmic and mitochondrial) directly contribute to the phenotype of the SM and SM-like cells involved in PH. Finally, we raise the possibility that SMCs transition from a proliferative to a senescent, pro-inflammatory and metabolically active phenotype over time.

CCR2/CCR5-mediated macrophage–smooth muscle cell crosstalk in pulmonary hypertension

Macrophages are major players in the pathogenesis of pulmonary arterial hypertension (PAH).

To investigate whether lung macrophages and pulmonary-artery smooth muscle cells (PASMCs) collaborate to stimulate PASMC growth and whether the CCL2-CCR2 and CCL5-CCR5 pathways inhibited macrophage–PASMC interactions and PAH development, we used human CCR5-knock-in mice and PASMCs from patients with PAH and controls.

Conditioned media from murine M1 or M2 macrophages stimulated PASMC growth. This effect was markedly amplified with conditioned media from M2 macrophage/PASMC co-cultures. CCR2, CCR5, CCL2 and CCL5 were upregulated in macrophage/PASMC co-cultures. Compared to inhibiting either receptor, dual CCR2 and CCR5 inhibition more strongly attenuated the growth-promoting effect of conditioned media from M2-macrophage/PASMC co-cultures. Deleting either CCR2 or CCR5 in macrophages or PASMCs attenuated the growth response. In mice with hypoxia- or SUGEN/hypoxia-induced PH, targeting both CCR2 and CCR5 prevented or reversed PH more efficiently than targeting either receptor alone. Patients with PAH exhibited CCR2 and CCR5 upregulation in PASMCs and perivascular macrophages compared to controls. The PASMC growth-promoting effect of conditioned media from M2-macrophage/PASMC co-cultures was greater when PASMCs from PAH patients were used in the co-cultures or as the target cells and was dependent on CCR2 and CCR5. PASMC migration toward M2-macrophages was greater with PASMCs from PAH patients and was attenuated by blocking CCR2 and CCR5.

CCR2 and CCR5 are required for collaboration between macrophages and PASMCs to initiate and amplify PASMC migration and proliferation during PAH development. Dual targeting of CCR2 and CCR5 may hold promise for treating human PAH.

The Search for Disease-Modifying Therapies in Pulmonary Hypertension

Pulmonary hypertension (PH) and its severe subtype pulmonary arterial hypertension (PAH) encompass a set of multifactorial diseases defined by sustained elevation of pulmonary arterial pressure and pulmonary vascular resistance leading to right ventricular failure and subsequent death. Pulmonary hypertension is characterized by vascular remodeling in association with smooth muscle cell proliferation of the arterioles, medial thickening, and plexiform lesion formation. Despite our recent advances in understanding its pathogenesis and related therapeutic discoveries, PH still remains a progressive disease without a cure. Nevertheless, development of drugs that specifically target molecular pathways involved in disease pathogenesis has led to improvement in life quality and clinical outcomes in patients with PAH. There are presently more than 12 Food and Drug Administration-approved vasodilator drugs in the United States for the treatment of PAH; however, mortality with contemporary therapies remains high. More recently, there have been exuberant efforts to develop new pharmacologic therapies that target the fundamental origins of PH and thus could represent disease-modifying opportunities. This review aims to summarize recent developments on key signaling pathways and molecular targets that drive PH disease progression, with emphasis on new therapeutic options under development.

Monocytic C-C chemokine receptor 5 expression increases in in vitro intermittent hypoxia condition and in severe obstructive sleep apnea patients

Purpose

Obstructive sleep apnea (OSA) patients have higher risk of cardiovascular disease. C-C chemokine receptor 5 (CCR5), as an important receptor for monocyte recruitment and the initiation of atherosclerosis, was studied under intermittent hypoxia and in OSA patients.

Methods

The expression and function of CCR5 regulated by intermittent hypoxia in monocytic THP-1 cells were investigated in an in vitro intermittent hypoxia culture system. The expression levels of protein and mRNA were analyzed by western blot and RT/real-time PCR analysis. Cell adhesion assay and transwell filter migration assay were carried out to investigate the adhesion and chemotaxis of monocytes. In addition, the mRNA expression of CCR5 in monocytes isolated from peripheral blood of 72 adults was analyzed.

Results

Intermittent hypoxia upregulated the expression of CCR5 in THP-1 cells and enhanced the adhesion and chemotaxis of monocytes to vascular endothelial cells mediated by RANTES. The CCR5 expression induced by intermittent hypoxia was inhibited by inhibitor for p42/44 MAPK. Besides, the expression of CCR5 in monocytes increased along the AHI value especially in severe OSA patients that was statistically significant compared with mild and moderate OSA groups.

Conclusions

This study demonstrated the increased monocytic CCR5 gene expression in patients with severe OSA. Intermittent hypoxia, the characteristic of OSA, induced monocytic CCR5 gene expression and the enhanced RANTES-mediated chemotaxis and adhesion through p42/44 MAPK signal pathways.

Nanoparticle-Mediated Targeting of Pitavastatin to Small Pulmonary Arteries and Leukocytes by Intravenous Administration Attenuates the Progression of Monocrotaline-Induced Established Pulmonary Arterial Hypertension in Rats

Statins are known to improve pulmonary arterial hypertension (PAH) by their anti-inflammatory and anti-proliferative effects in animal models. However, recent clinical studies have reported that clinically approved statin doses failed to improve clinical outcomes in patients with PAH. We therefore hypothesized that nanoparticle (NP) -mediated targeting of pitavastatin could attenuate the progression of established PAH.We induced PAH by subcutaneously injecting monocrotaline (MCT) in Sprague-Dawley rats. On day 14 after the MCT injection, animals that displayed established PAH on echocardiography were included. On day 17, they were randomly assigned to the following 5 groups: daily intravenous administration of (1) vehicle, (2) fluorescein-isothiocyanate-NP, (3) pitavastatin, (4) pitavastatin-NP, or (5) oral sildenafil. Intravenous NP was selectively delivered to small pulmonary arteries and circulating CD11b-positive leukocytes. On day 21, pitavastatin-NP attenuated the progression of PAH at lower doses than pitavastatin alone. This was associated with the inhibition of monocyte-mediated inflammation, proliferation, and remodeling of the pulmonary arteries. Interestingly, sildenafil attenuated the development of PAH, but had no effects on inflammation or remodeling of the pulmonary arteries. In separate experiments, only treatment with pitavastatin-NP reduced the mortality rate at day 35.NP-mediated targeting of pitavastatin to small pulmonary arteries and leukocytes attenuated the progression of established MCT-induced PAH and improved survival. Therapeutically, pitavastatin-NP was associated with anti-inflammatory and anti-proliferative effects on small pulmonary arteries, which was completely distinct from the vasodilatory effect of sildenafil. Pitavastatin-NP can be a novel therapeutic modality for PAH.

Macrophage Immunomodulation: The Gatekeeper for Mesenchymal Stem Cell Derived-Exosomes in Pulmonary Arterial Hypertension?

Pulmonary arterial hypertension (PAH) is a progressive disease characterized by remodeling of the pulmonary arteries, increased pulmonary infiltrates, loss of vascular cross-sectional area, and elevated pulmonary vascular resistance. Despite recent advances in the management of PAH, there is a pressing need for the development of new tools to effectively treat and reduce the risk of further complications. Dysregulated immunity underlies the development of PAH, and macrophages orchestrate both the initiation and resolution of pulmonary inflammation, thus, manipulation of lung macrophage function represents an attractive target for emerging immunomodulatory therapies, including cell-based approaches. Indeed, mesenchymal stem cell (MSC)-based therapies have shown promise, effectively modulating the macrophage fulcrum to favor an anti-inflammatory, pro-resolving phenotype, which is associated with both histological and functional benefits in preclinical models of pulmonary hypertension (PH). The complex interplay between immune system homeostasis and MSCs remains incompletely understood. Here, we highlight the importance of macrophage function in models of PH and summarize the development of MSC-based therapies, focusing on the significance of MSC exosomes (MEx) and the immunomodulatory and homeostatic mechanisms by which such therapies may afford their beneficial effects.

Blockade of the chemokine receptor, CCR5, reduces the growth of orthotopically injected colon cancer cells via limiting cancer-associated fibroblast accumulation

We previously demonstrated that cancer-associated fibroblasts (CAFs) accumulate at tumor sites through the interaction between a chemokine, CCL3, and its receptor, CCR5, in the late phase of colitis-associated colon carcinogenesis. Here we examined the effect of a CCR5 antagonist, maraviroc, on tumor growth arising from the orthotopic injection of mouse or human colon cancer cell lines into the cecal wall by focusing on CAFs. Orthotopic injection of either cell line caused tumor formation together with leukocyte infiltration and fibroblast accumulation. Concomitant oral administration of maraviroc reduced tumor formation with few effects on leukocyte infiltration. In contrast, maraviroc reduced the intratumor number of α-smooth muscle actin-positive fibroblasts, which express epidermal growth factor, a crucial growth factor for colon cancer cell growth. These observations suggest that maraviroc or other CCR5 antagonists might act as novel anti-CRC drugs to dampen CAFs, an essential cell component for tumor progression.

Emerging therapeutics in pulmonary hypertension

Pulmonary hypertension (PH) is a progressive and often fatal illness presenting with nonspecific symptoms of dyspnea, lower extremity edema, and exercise intolerance. Pathologically, endothelial dysfunction leads to abnormal intimal and smooth muscle proliferation along with reduced apoptosis, resulting in increased pulmonary vascular resistance and elevated pulmonary pressures. PH is subdivided into five World Health Organization groups based on the disease pathology and specific cause. While there are Food and Drug Administration-approved medications for the treatment of pulmonary arterial hypertension (PAH; Group 1 PH), as well as for chronic thromboembolic PH (Group 4 PH), the morbidity and mortality remain high. Moreover, there are no approved therapies for other forms of PH (Groups 2, 3, and 5) at present. New research has identified molecular targets that mediate vasodilation, anti-inflammatory, and antifibrotic changes within the pulmonary vasculature. Given that PAH is the most commonly studied form of PH worldwide and because recent studies have led to better mechanistic understanding of this devastating disease, in this review we attempt to provide an updated overview of new therapeutic approaches under investigation for the treatment of PH, with a particular focus on PAH, as well as to offer guidelines for future investigations.

CCL5 deficiency rescues pulmonary vascular dysfunction, and reverses pulmonary hypertension via caveolin-1-dependent BMPR2 activation

Pulmonary arterial hypertension (PAH) is a devastating cardiopulmonary disorder characterized by pulmonary arterial remodeling mainly due to excess cellular proliferation and apoptosis resistance of pulmonary arterial smooth muscle cells (PASMCs). Reduced bone morphogenetic protein receptor 2 (BMPR2) expression in patients with PAH impairs pulmonary arterial endothelial cells (PAECs) function. This can adversely affect PAEC survival and promote PASMCs proliferation. We hypothesized that interventions to normalize the expression of genes that are targets of the BMPR2 signaling could restore PAECs function and prevent or reverse PAH. Here we characterized for the first time, in human PAECs, chemokine (C-C motif) ligand 5 (CCL5/RANTES) deficiency restore BMP-mediated PAECs function. In the cell culture experiments, we found that CCL5 deficiency increased apoptosis and tube formation of PAECs, but suppressed proliferation and migration of PASMCs. Silencing CCL5 expression in PAH PAECs restored bone morphogenetic protein (BMP) signaling responses and promoted phosphorylation of SMADs and transcription of ID genes. Moreover, CCL5 deficiency inhibited angiogenesis by increasing pSMAD-dependent and-independent BMPR2 signaling. This was linked mechanistically to enhanced interaction of BMPR2 with caveolin-1 via CCL5 deficiency-mediated stabilization of endothelial surface caveolin-1. Consistent with these functions, deletion of CCL5 significantly attenuated development of Sugen5416/hypoxia-induced PAH by restoring BMPR2 signaling in mice. Taken together, our findings suggest that CCL5 deficiency could reverse obliterative changes in pulmonary arteries via caveolin-1-dependent amplification of BMPR2 signaling. Our results shed light on better understanding of the disease pathobiology and provide a possible novel target for the treatment of PAH.

The HIV co-receptor CCR5 regulates osteoclast function

C–C chemokine receptor 5 (CCR5) is a co-receptor of HIV. Epidemiological findings suggest that the functional loss of CCR5 is correlated with a lower incidence of bone-destructive diseases as well as of HIV transmission. However, it is not clear whether CCR5 is involved in regulation of the function of bone cells, in addition to that of immune cells. Here we show that blockade of CCR5 using specific antibodies impairs human osteoclast function in vitro. Ccr5-deficient (Ccr5^−/−) mice presented with dysfunctional osteoclasts and were resistant to osteoporosis induced by receptor activator of nuclear factor kappa-B ligand (RANKL), which triggers osteoporosis independently of inflammatory and immunomodulatory pathways. Furthermore, Ccr5 deficiency impairs the cellular locomotion and bone-resorption activity of osteoclasts, which is associated with the disarrangement of podosomes and adhesion complex molecules including Pyk2. Overall, the data provides evidence that CCR5 has an essential role in bone-destructive conditions through the functional regulation of osteoclasts.

CCR5 is a co-receptor for HIV, and loss of function is associated with lower incidence of HIV but also with bone-destructive diseases. Here the authors show that ablation of CCR5 impairs osteoclast function and improves resistance to osteoporosis in mouse models.

Roles for the CX3CL1/CX3CR1 and CCL2/CCR2 Chemokine Systems in Hypoxic Pulmonary Hypertension

Monocytes/macrophages are major effectors of lung inflammation associated with various forms of pulmonary hypertension (PH). Interactions between the CCL2/CCR2 and CX3CL1/CX3CR1 chemokine systems that guide phagocyte infiltration are incompletely understood. Our objective was to explore the individual and combined actions of CCL2/CCR2 and CX3CL1/CX3CR1 in hypoxia-induced PH in mice; particularly their roles in monocyte trafficking, macrophage polarization, and pulmonary vascular remodeling. The development of hypoxia-induced PH was associated with marked increases in lung levels of CX3CR1, CCR2, and their respective ligands, CX3CL1 and CCL2. Flow cytometry revealed that both inflammatory Ly6C^hi and resident Ly6C^lo monocyte subsets exhibited sustained increases in blood and a transient peak in lung tissue, and that lung perivascular and alveolar macrophage counts showed sustained elevations. CX3CR1^-/- mice were protected against hypoxic PH compared with wild-type mice, whereas CCL2^-/- mice and double CX3CR1^-/-/CCL2^-/- mice exhibited similar PH severity, as did wild-type mice. The protective effects of CX3CR1 deficiency occurred concomitantly with increases in lung monocyte and macrophage counts and with a change from M2 to M1 macrophage polarization that markedly diminished the ability of conditioned media to induce pulmonary artery smooth muscle cell (PA-SMC) proliferation, which was partly dependent on CX3CL1 secretion. Results in mice given the CX3CR1 inhibitor F1 were similar to those in CX3CR1^-/- mice. In conclusion, CX3CR1 deficiency protects against hypoxia-induced PH by modulating monocyte recruitment, macrophage polarization, and PA-SMC cell proliferation. Targeting CX3CR1 may hold promise for treating PH.

Extracellular Calpain/Calpastatin Balance Is Involved in the Progression of Pulmonary Hypertension

Excessive growth of pulmonary arterial (PA) smooth muscle cells (SMCs) is a major component of PA hypertension (PAH). The calcium-activated neutral cysteine proteases calpains 1 and 2, expressed by PASMCs, contribute to PH but are tightly controlled by a single specific inhibitor, calpastatin. Our objective was to investigate calpastatin during pulmonary hypertension (PH) progression and its potential role as an intracellular and/or extracellular effector. We assessed calpains and calpastatin in patients with idiopathic PAH and mice with hypoxic or spontaneous (SM22-5HTT(+) strain) PH. To assess intracellular and extracellular roles for calpastatin, we studied effects of the calpain inhibitor PD150606 on hypoxic PH in mice with calpastatin overexpression driven by the cytomegalovirus promoter (CMV-Cast) or C-reactive protein (CRP) promoter (CRP-Cast), inducing increased calpastatin production ubiquitously and in the liver, respectively. Chronically hypoxic and SM22-5HTT(+) mice exhibited increased lung calpastatin and calpain 1 and 2 protein levels and activity, both intracellularly and extracellularly. Prominent calpastatin and calpain immunostaining was found in PASMCs of remodeled vessels in mice and patients with PAH, who also exhibited increased plasma calpastatin levels. CMV-Cast and CRP-Cast mice showed similarly decreased PH severity compared with wild-type mice, with no additional effect of PD150606 treatment. In cultured PASMCs from wild-type and CMV-Cast mice, exogenous calpastatin decreased cell proliferation and migration with similar potency as PD150606 and suppressed fibronectin-induced potentiation. These results indicate that calpastatin limits PH severity via extracellular mechanisms. They suggest a new approach to the development of treatments for PH.

A Time- and Compartment-Specific Activation of Lung Macrophages in Hypoxic Pulmonary Hypertension

Studies in various animal models suggest an important role for pulmonary macrophages in the pathogenesis of pulmonary hypertension (PH). Yet, the molecular mechanisms characterizing the functional macrophage phenotype relative to time and pulmonary localization and compartmentalization remain largely unknown. In this study, we used a hypoxic murine model of PH in combination with FACS to quantify and isolate lung macrophages from two compartments over time and characterize their programing via RNA sequencing approaches. In response to hypoxia, we found an early increase in macrophage number that was restricted to the interstitial/perivascular compartment, without recruitment of macrophages to the alveolar compartment or changes in the number of resident alveolar macrophages. Principal component analysis demonstrated significant differences in overall gene expression between alveolar and interstitial macrophages (IMs) at baseline and after 4 and 14 d hypoxic exposure. Alveolar macrophages at both day 4 and 14 and IMs at day 4 shared a conserved hypoxia program characterized by mitochondrial dysfunction, proinflammatory gene activation, and mTORC1 signaling, whereas IMs at day 14 demonstrated a unique anti-inflammatory/proreparative programming state. We conclude that the pathogenesis of vascular remodeling in hypoxic PH involves an early compartment-independent activation of lung macrophages toward a conserved hypoxia program, with the development of compartment-specific programs later in the course of the disease. Thus, harnessing time- and compartment-specific differences in lung macrophage polarization needs to be considered in the therapeutic targeting of macrophages in hypoxic PH and potentially other inflammatory lung diseases.

Non-infectious pulmonary disorders in HIV

INTRODUCTION

Since the advent of antiretroviral therapy (ART), non-infectious pulmonary disorders have become common comorbidities in the human immunodeficiency virus (HIV) positive population. Clinicians caring for those with HIV disease should be aware of the prevalence of non-infectious pulmonary disorders. A comprehensive understanding is required to diagnosis and manage these syndromes appropriately. Areas covered: This review focuses on the epidemiology, risk factors, pathogenesis, clinical feature and diagnosis, and treatment of HIV-related chronic obstructive pulmonary disease (COPD), lung cancer, pulmonary hypertension. Expert Commentary: The prevalence of COPD in the HIV population is frequent and requires appropriate diagnosis and treatment. HIV-positive individuals with lung cancer carry a poorer prognosis and require early diagnosis and treatment. A complex condition exists with pulmonary hypertension in the HIV population and requires a high degree of clinical suspicion for early diagnosis.

Maintaining lung health with longstanding HIV

PURPOSE OF REVIEW

Human immunodeficiency virus (HIV) is now managed as a chronic disease. Non-infectious pulmonary conditions have replaced infection as the biggest threat to lung health, particularly as HIV cohorts age, but there is no consensus on how best to maintain long-term lung health. We review the epidemiology and pathogenesis of chronic obstructive pulmonary disease (COPD), pulmonary arterial hypertension (PAH), and lung cancer in HIV-seropositive individuals.

RECENT FINDINGS

Diagnoses of COPD are now up to 50% more prevalent in HIV-seropositive individuals than HIV-uninfected controls, and prospective pulmonary function studies find significant impairment in 7% to more than 50% of HIV-seropositive individuals. The prevalence of HIV-PAH is 0.2-0.5%, and lung cancer is two to three times more prevalent in HIV-seropositive individuals. Although host factors such as age and smoking have a role, HIV is an independent contributor to the pathogenesis of COPD, PAH, and lung cancer. Chronic inflammation, immune senescence, oxidative stress, and direct effects of viral proteins are all potential pathogenetic mechanisms. Despite their prevalence, non-infectious lung diseases remain underrecognized and evidence for effective screening strategies in HIV-seropositive individuals is limited.

SUMMARY

COPD, PAH, and lung cancer are a growing threat to lung health in the highly active antiretroviral therapy era necessitating early recognition.